This invention relates to compaction devices for fiber placement machines, and more particularly to a multi-segment, curvilinearly conformal compaction roller for a fiber placement machine which is capable of applying a generally uniform pressure against a complexly shaped tool mounted in the machine, and wherein its independent segments can move laterally slightly in a manner which does not interfere with other components of the machine disposed closely adjacent the roller during operation of the machine.
Fiber placement machines typically employ a compaction device (i.e., a compaction xe2x80x9cheadxe2x80x9d) to compact a band of uncured epoxy impregnated composite towpreg onto a tool surface mounted in the machine. A conformal roller is required to provide adequate compaction pressure across the entire width of the material as the material is drawn over a tool having a contoured (i.e., complexly) shaped surface.
The problem with present day fiber placement machines and the conformal rollers typically used therewith is that the roller must be able to conform to the tool surface. Poor compaction allows the material to pull away from the tool and therefore require costly and time consuming hand repairs to be made. Accordingly, some form of conformal roller is required to compact the band of material over a complexly shaped tool surface of the fiber placement machine, thus ensuring even compaction forces across the width of the material being fed through the machine.
The problem with implementing the use of a conformal roller in many forms of fiber placement machines is the very limited space available in the area of the machine where the roller is to be supported. More often, these severe geometric constraints severely limit how the roller can conform without interfering with other components of the machine disposed closely adjacent the roller. FIG. 1 illustrates this problem if the entire roller is moved linearly to conform to a complexly shaped tool surface. In FIG. 1 it will be noted that the roller R interferes at points 1 and 2 with components A and B of a fiber placement machine C. With some types of fiber placement machines, implementation of a roller design incorporating linearly translating segments, such as shown in FIG. 1, would result in the segments colliding with other head components of the machine. This can prevent the full conformance required to maintain even compaction force over complex contours of he tool, thus causing damage to fragile lay-ups such as sandwich lay-ups. It can also result in potential jamming of the roller segments causing them to slide along the surface of the material being compacted, thus causing damage to the outer segment surface and lay-up.
Various attempts have been made to develop conformal rollers using internal pressure bladders. Two such attempts are disclosed in U.S. Pat. Nos. 4,052,246 and 4,341,584. Fiber placement specific conformal devices incorporating internal bladders and linearly translating roller segments were also disclosed in U.S. Pat. Nos. 5,454,897 and 5,110,395. The teachings of these four patents are expressly incorporated by reference herein. While the conformal devices disclosed in these patents may be acceptable in some applications and with certain types of fiber placement machines, these devices are still limited by the additional space required by the linearly translating roller segments of each, which space is not always available with every make of fiber placement machine.
It is therefore a principal object of the present invention to provide a conformal compaction roller for use with a fiber placement machine which does not require the additional space needed by linearly translating roller segments, and which can therefore be used with fiber placement machines having a very limited space envelope within which the compaction roller must operate.
It is still another object of the present invention to provide a conformal compactional roller for a fiber placement machine that does not require modification to standard components of the fiber placement machine, and which can therefore be installed on an existing fiber placement machine without otherwise affecting operation of other components of the machine.
It is still another object of the present invention to provide a conformal compaction roller for a fiber placement machine which can operate within a much smaller space envelope than linearly translatable roller devices, and which still applies a generally uniform pressure across a complexly shaped tool surface of the machine.
It is still another object of the present invention to provide a compaction roller capable of providing a longer stroke length for a given diameter compaction roller than a compaction roller having linearly translating roller segments.
The above and other objects are provided by a conformal compaction roller in accordance with preferred embodiments of the present invention. The compaction roller is adapted for use with fiber placement machines having a small space envelope within which the roller must operate, and which envelope would not permit the use of linearly translatable compaction rollers. The compaction roller of the present invention thus can be used in those fiber placement machines where a linearly translatable compaction roller could not be installed because of interference that would result from other components of the machine disposed closely adjacent to the compaction roller.
The compaction roller of the present invention generally comprises a plurality of roller segments disposed in a side-by-side relationship, and each being supported for pivotable movement about an eccentrically disposed pivot shaft. Each roller segment further includes an arcuate shaped cutout. Collectively, the cutouts of the roller segments form an arcuate bore. Disposed within the arcuate bore is a strong back member which is supported by a pair of end plates. The end plates are in turn operatively supported by portions of the fiber placement machine with which the compaction roller is being used.
Also disposed within the arcuate bore is at least one bladder having a length that is sufficient to extend through each of the roller segments. The bladder is disposed against the strong back member and, when inflated with air or another fluid medium, causes the roller segments to be urged pivotally about the eccentrically disposed pivot shaft against the tool surface which is mounted in the fiber placement machine. Since the roller segments do not translate linearly, each roller segment is able to move slightly to conform to the complexly shaped tool surface without impinging other components of the machine disposed closely adjacent to the compaction roller.
Each roller segment further includes a bearing assembly disposed on an outer perimeter thereof. A tire is in turn disposed on the outer race of each bearing assembly of each roller segment. In one preferred form, each tire comprises an elastomeric member. The bearing assemblies enable the tire of each roller segment to move rotationally relative to its associated roller segment.
The independent, eccentric, pivoting movement of each roller segment thus enables each of the segments to conform to a complexly shaped tool surface without moving so much as to cause interference with other components of the fiber placement machine that are disposed very close to the compaction roller. This pivoting movement also allows sufficient conformance to provide uniform compaction pressures across the entire compaction roller. The compaction roller of the present invention can thus be used with fiber placement machines where the use of a compaction roller having linearly translating roller segments would not be possible because of interference of the roller segments with other components of the fiber placement machine disposed close to the compaction roller.
The compaction roller of the present invention further does not require significant modification of the fiber placement machine. As such, the compaction roller of the present invention can be retrofitted on a fiber placement machine to thus allow operation in connection with various complexly shaped tool surfaces, where such operation would not be possible with linearly translatable compaction rollers.